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Abstract

Background

Body image disturbance is a core feature of anorexia nervosa (AN). Attitudinal and
cognitive biases as well as fundamental perceptual differences have been hypothesized
to play a role in this disturbance.

Results

As predicted, participants with AN scored significantly higher on body dissatisfaction,
perfectionism measures and had greater body distortion (as assessed by a body size
estimation task). Cognitive–affective factors and perfectionism were highly correlated
with body image distortion in AN. No significant differences were found between groups
on the generic perception task.

Conclusions

Findings did not confirm the hypothesis of fundamental perceptual inefficiencies in
body image disturbance in individuals with AN. Despite renewed interest in fundamental
perceptual factors implicated in body image disturbance, these findings suggest that
it continues to be important to focus treatment on cognitive affective biases versus
fundamental perceptual inefficiencies.

Keywords:

Background

Body image disturbance is one of the diagnostic criteria [1] for Anorexia Nervosa (AN), and has been implicated in both the development [2,3] and maintenance [4] of eating disorders. Furthermore, body image disturbances often persist following
recovery (e.g. [5]) and predict relapse [6]. Such disturbance can manifest as disturbance of percept (i.e. distortion) and concept
(i.e. dissatisfaction).

A growing consensus exists that two types of body representation may be impaired in
AN: the body schema and the body image (for reviews: [7,8]). The body schema is defined as a sensorimotor representation of the body in action
– whether this action is actual, anticipated or imagined [9]. The body image, by contrast, consists of several components, subdivided into the
perceptual (sensory perception) and the attitudinal (cognitive and affective factors).
These body image representations are not used for action, though may influence and
be influenced by the body schema.

Distortions in either the body schema or the body image could result in body size
overestimation. Recent research in eating disorders has focused on attitudinal components
of body image disturbance, with individuals with AN showing higher levels of body
dissatisfaction than healthy controls ([10]; see [11] for a review). However, there has been a resurgence of interest in the role of perceptual
disturbances of body representations. Benninghoven et al. [12] found increased body size overestimation in women with eating disorders, but no impairment
of estimation of other women’s bodies, nor of male ideals of female body attractiveness,
concluding that body distortion was confined to the processing of ‘self-referential’
information, rather than body image information in general. Further, there have been
findings of sub-optimal visuo-spatial performance in individuals with AN, on subtests
of the Wechsler Adult Intelligence Scale [13] and the Rey–Osterreith Complex Figure (ROCF; Meyers & [14]). In some, these difficulties persist after weight recovery (e.g. [15]). Visuo-spatial performance has also been shown to correlate with body size estimation
in the general population using the Adjustable Light Beam Apparatus [16]. However, visual body image disturbance has also been found to result from distortions
of memory rather than perception [17], supporting the role of attitudinal rather than perceptual influences on body image
disturbance. Interoceptive awareness (bodily perception of physiological sensations)
may also be impaired in AN (e.g. [18]).

Another form of bodily awareness, haptic perception (a form of tactile perception),
is defined as the recognition of external stimuli, through the combination of somatosensory
and proprioceptive perception [19]. Haptic perceptual impairment has been noted in individuals with AN, with inefficiencies
in haptic set shifting tasks [20,21]. Childhood perfectionism is also associated with sub-optimal performance on neuropsychological
measures of set-shifting (i.e. difficulties in responding effectively to rule changes)
[20,22,23] and is a personality trait linked to an increased risk of developing an eating disorder
[24].

Further haptic-perceptual impairment was noticed in somatosensory tasks [25] persisting across states of illness and recovery, suggesting that this may be a trait
factor in the disorder. Grunwald et al. [26] also found impairment in performance on a bimanual somatosensory task, the Angle
Paradigm Task, in adolescents with AN. The impaired performance was only significant
on right-handed tasks, which Grunwald and colleagues related to a right parietal lobe
dysfunction, using the direct access theory of perceptual processing [27]. Differential activation of the parietal cortex has been implicated in the presentation
of AN (e.g. [28]) and is the area of the brain most consistently associated with the disorder in the
functional neuroimaging literature [29].

The parietal lobe is also thought to be responsible for the integration of proprioceptive
and visual information regarding one’s own body, with this integration forming the
basis of the physical body representation (schema; [30]). Disorders of body image have been associated with both left and right parietal
lobes, but little is known about the neural correlates of body image in AN, particularly
with regard to laterality. Some have found differential activation in the left hemisphere
[17,31], and others the right hemisphere (e.g. [32]). Neuroimaging studies investigating body dissatisfaction and distortion in AN have
found links with parietal lobe function [31,33]. Indirect associations with parietal lobe dysfunction have been postulated in studies
which found sub-optimal visual and tactile performance in AN [10,34], but no study, to our knowledge, has yet explored the interactions of haptic perception,
body image dissatisfaction and distortion together in relation to perfectionism.

This study therefore first explored haptic perceptual task performance in individuals
with a current diagnosis of AN as compared to age-matched controls; secondly, the
attitudinal and perceptual aspects of body image disturbance, and their relative contribution
to body image distortion in AN were investigated.

The following hypotheses were tested: 1) individuals with AN would make greater body
size estimation (BSE) errors than healthy controls (HC); 2) individuals with AN would
have greater body dissatisfaction than HC; 3) individuals with AN would perform worse
than HC on a measure of haptic perception; 4) the AN group would score more highly
on measures of perfectionism compared to HC individuals; and 5) correlations would
exist between attitudes to body image, haptic perception, perfectionism and distorted
body image in the AN group.

Method

Participants

Sixty-one adult females were recruited to the study. Thirty females with a clinical
diagnosis of AN or EDNOS-AN were recruited from eating disorder services of hospitals
in South London. Diagnosis was made by trained clinicians using a semi-structured
interview schedule and DSM-IV criteria. Thirty-one age-matched females were recruited
to the HC group. A screening questionnaire confirmed the absence of diagnosed eating
disorders and other psychiatric disorders. Study volunteers with an intellectual disability,
head injury or non-fluent English were excluded from the study.

Materials and procedure

Procedure

Participants were asked to read the information sheet, sign the consent form and complete
the screening form. The study was approved by a National Health Service ethics committee.
The self-report measures were completed followed by the perceptual tasks.

Self-Report/attitudinal measures

The Silhouettes Body Perception Scale[35] is an attitudinal measure of body image, using a scale of silhouettes increasing
in size. Participants mark the silhouette that best corresponds with their current
body shape, in their view, and the silhouette that matches how they would wish to
look. To measure the level of body dissatisfaction, the score from item 2 ‘how you
would wish to look’ is subtracted from the score from item 1 ‘your current body shape’.
A score of 0 represents no body dissatisfaction, a positive number score represents
a desire for a smaller body shape and a negative number score represents a desire
for a larger body shape.

The scale has satisfactory test-retest reliability (r = .82) and convergent validity (r = .73) in multi-ethnic general populations, with acceptable discriminative power
in differentiating between samples [35].

The Body Image Avoidance Questionnaire (BIAQ; [36]) is a nineteen-item self-report behavioural measure of body image, assessing behaviours
associated with a negative body image, such as avoidance of situations that provoke
concern about physical appearance. Participants respond on a scale of 0 (never) to
5 (always). In this study it was used as an additional measure of body dissatisfaction.

The BIAQ has proven psychometric properties in clinical and non-clinical populations
[36] with good internal consistency (Cronbach’s alpha of .89), as well as showing modest
associations with body size estimation tasks (r = .22, p < .01), strong associations with negative attitudes to weight and shape (r = .78, p < .0001). Furthermore, it distinguishes satisfactorily between clinical and non-clinical
populations [36], as well as responding to change resulting from treatment of eating disorders.

The Eating Disorders Examination-Questionnaire (EDE-Q; [37]) is a self-report measure of eating disorder symptomatology. It consists of twenty-eight
items, asking participants to mark to which degree they have engaged in each behaviour
over the previous 28 days. The questionnaire predominantly consists of scale items
of 0-6, with a higher score indicating a greater intensity or frequency. There are
four subscales: Dietary Restraint, Eating Concern, Weight Concern, and Shape Concern.
The Weight and Shape Concern subscales were used in this study as a measure of body
image.

The EDE-Q’s internal consistency (Cronbach’s α = .78 - .93), temporal stability and
test-retest reliability (r = .81- .94) have been established in assessing the core attitudinal features of eating
disorders [38-40]. It has been validated as a screening tool to detect eating disorders in community
samples [39] and in primary care [41].

The Frost Multi-dimensional Perfectionism Scale (FMPS; [42]) is a self-report, 35-item, multi-dimensional measure of perfectionist traits, which
generates an overall perfectionism score. Scores for six subscales reflecting various
domains of perfectionism can also be calculated: concern over mistakes, doubts about
actions, personal standards, parental expectations, parental criticism and organization.
The total perfectionism score is the sum of all subscales. Frost et al. [42,43] have reported good reliability of the subscales (Cronbach’s α = .77 to .93) and good
concurrent validity with other perfectionism scales as well as good construct validity
in relation to a variety of measures of psychopathology. Strong validity was also
shown by Enns & Cox [44]. This measure is also widely reported in the eating disorder literature (e.g. [45]).

Perceptual measures

The Adjustable Light Beam Apparatus (ALBA; [46]) is an experimental task measuring an individual’s accuracy in estimating ones own
body size. An overhead projector, with the apparatus attached, is placed at 1.5 metres
from a blank wall. Participants adjust rods on the apparatus to beam rays of light
on to the wall. Each beam of light is used to approximate the width of four body parts
in turn (cheeks, waist, hips and thighs). A type of silhouette is created, the entirety
of which can be adjusted if desired. Measurements of the width of the beam were taken
from the wall, and secondary measurements of the width of the gap on the apparatus
itself were also taken. This second measurement is converted to a full-scale measurement
using the formula outlined in the original paper [46]. Actual measurements of the waist, hips and thighs were then taken using calipers.
Cheek measurements were not taken, as this anchor point is used as a practice item,
and was not found to correlate well with the other body sites, in the original study.
The two sets of recordings were compared to provide a calculation of accuracy in BSE.
The measure has shown good test-retest reliability in women, in terms of constancy
of overestimation over time (over 1 week) and discriminant validity between size estimation
and size dissatisfaction, as well as between size estimation and overall satisfaction
with appearance.

The Angle Paradigm Task[26] is a sensorimotor perception task, measuring haptic perception. In this bimanual
task, one metal rod is always placed at 90° and the other rod placed at another angle.
Participants were blindfolded and adjusted the first metal bar, set at 90°, so that
it was either parallel or mirror image to the second bar. There were four conditions
in the task: adjusting the angle as a parallel with the right hand, and then with
the left hand, and adjusting the angle as a mirror image with the right hand, and
then with the left hand. For each condition there were five trials, with the metal
bar set at 45°, 22°, 65°, 15° and 35°. Before each condition participants were given
the opportunity to practice the task once with the blindfold on, but without any visual
feedback. The outcome measure for the task was the difference between the angles of
the set and adjusted bars. The mean of the total time taken to adjust each angle was
used as an additional measure of perfectionism, as in the original paper. Left-handed
individuals are excluded from this task, as the original study looked at only right-handed
individuals. The task is intended to explore the theorised right parietal dysfunction
in AN, and it is posited that a left-handed individual is not likely to experience
the same demands on the right parietal cortex in this task as a right-handed individual.

Statistical analysis

All data were analysed using SPSS Statistics 20 software. Independent t-tests were used to compare the two groups on demographic characteristics and eating
disorder symptomatology variables (EDE-Q v.4 and BMI in kg/m2). Cohen’s d (mean1 - mean2/pooled standard deviation) was calculated to provide a measure of
effect size where appropriate, with effect sizes of ≤ 0.2 defined as small, ≥ 0.5
defined as medium and ≥ 0.8 defined as large.

Independent t-tests compared the AN and HC groups on their scores on the self-report and experimental
measures of body image perception, haptic perception and perfectionism, to explore
differences on these measures.

Correlational analyses were performed separately on the clinical and HC data to explore
possible relationships between variables within each group, using Pearson’s Product
Moment correlation coefficients (r), or Spearman’s rho where data were not normally distributed, and focusing on relationships
between the ALBA as a measure of body image distortion, with the haptic perception
tasks and with the attitudinal measures.

Alpha was set at p < 0.05. Corrections to address the family-wise error rate in multiple
analyses were carried out using Hochberg’s correction, as a less conservative method
than Bonferroni’s correction method [47].

Results

Participant characteristics

Three HC participants were excluded because of possible caseness due to low BMI or
clinical scores on the EDE-Q. One HC and four AN participants were excluded from the
angle paradigm task analysis owing to left-handedness. The final data analysis included
28 in the HC group and 30 in the AN group. For analyses including the Angle Paradigm
task, there were 27 in the HC group and 26 in the AN group.

Demographic and clinical data

As expected, there was no significant difference between groups on age. Also as expected,
the AN group had a significantly lower BMI than the HC group (t56= 9.70, p <. 01), and scored significantly higher on the global scale of the EDE-Q (t56= -10.53, p < .01).

Self-report measures: body dissatisfaction & attitudinal factors

Descriptive statistics for the self-report measures are shown in Table 1.

Body dissatisfaction

Using the Silhouette task, all individuals in the HC group either were satisfied with
their perceived size (25%; 7/28), or desired a smaller figure (75%; 21/28). 40% (12/30)
of individuals in the AN group expressed a desire for a larger figure. A further 10%
(3/30) of individuals in the AN group were satisfied with their perceived body size,
thus 50% (15/30) expressed a desire for a smaller figure. As well as these between-group
differences in the direction of desired change, the overall disparity between perceived
and desired silhouette, ignoring the direction of desired body shape change, was significantly
different, with the AN group significantly more dissatisfied with their bodies (p = .02).

On the BIAQ, the AN group showed significantly greater body dissatisfaction through
behavioural expression (t40.05 = -6.91, p < .01). A similar finding was reported on the weight and shape subscales of the EDE-Q,
with the AN group showing significantly greater Shape concern (t56 = -9.19, p < .01) and Weight concern (t47.18 = -7.84, p < .01).

Perfectionism

On the FMPS, the AN group scored significantly higher on the overall score, as expected
(t49.19= -7.78, p < .01). Analyses of subscales were not carried out, owing to lack of power. The perfectionism
score was positively correlated with the exploration time on the Angle Paradigm Task,
in the AN group only (r = .39, p = .03), meaning that the higher the perfectionism score, the longer the time taken
to complete the task.

Perceptual measures: haptic perception and body distortion

Descriptive statistics and pairwise comparisons for the experimental (perceptual)
measures are shown in Table 2.

BSE: body distortion

On the BSE task, using the Adjustable Light Beam Apparatus, two levels of analysis
were undertaken, first looking at estimation accuracy without direction (pure accuracy),
and secondly with direction (over or under-estimation). When the data were analysed
without the direction of inaccuracy, the AN group overestimated their bodies more
than the HC group overall, at waist, thighs and hips. The differences remained when
the data were analysed with the direction of inaccuracy.

Perceptual measures: haptic perception

Differences between groups on the Angle Paradigm task were explored using Independent
samples t tests. No significant group differences were found on any conditions of the task.
Group differences were found on total exploration time taken to complete the tasks,
however, with the AN group taking significantly longer than the HC group (t30.05 = 4.84, p < .01).

Further analysis of the AN group was carried out to determine if severity of illness
(as indicated by BMI and EDE-Q global score) was associated with performance on the
Angle Paradigm task. No significant correlations were found between EDE-Q and haptic
task performance. No significant correlations between BMI and Angle Paradigm tasks
were found after Hochberg’s step up corrections for multiple testing. However, prior
to correcting, a trend was found towards associations between the left-hand tasks
and BMI, which might warrant further investigation in future studies.

Exploring relationships with BSE

To investigate the relationship of perceptual versus attitudinal factors with BSE
accuracy in AN, correlations between the variables in these two broad domains with
BSE accuracy (with direction) were performed, using Pearson’s correlation coefficients
for normally distributed variables and Spearman’s correlation coefficients for variables
with skewed distributions. As multiple analyses were conducted, Hochberg’s step-up
adjustment for significance was used within each domain (attitudinal or perceptual).

A diagrammatic representation of the significant relationships of variables to body
distortion (BSE, with direction of inaccuracy) in the AN group is displayed in Figure 1.

None of the other perceptual measures was significantly correlated with performance
on the BSE task, whereas all the attitudinal measures significantly correlated with
BSE.

A strong relationship was found between body dissatisfaction (with direction) and
body distortion – the smaller the desired body shape, the greater the overestimation
of body size. The score on the shape subscale of the EDE-Q was significantly related
to the degree of overestimation – the higher the shape concern, the greater the overestimation.
Scores on the BIAQ and FMPS were also significantly related to BSE – as the degree
of body image avoidance increases, so does the degree of overestimation. Similarly,
as the rating of perfectionist traits increases, so does the degree of overestimation.

Original and adjusted p values, using Hochberg’s step-up method are presented in Table 3.

Discussion

As expected, individuals with AN demonstrated higher levels of body image distortion
as indicated by higher BSE errors on the Light Beam Apparatus, which confirms our
hypothesis that AN individuals would overestimate their body size more than healthy
controls. Additionally the AN group showed higher levels of body dissatisfaction than
the HC group, through a number of self report measures, supporting previous findings
[10].

Contrary to our hypothesis, previously reported haptic perception impairments in AN
were not supported by our findings, with no significant difference between the AN
and HC groups.

This difference may be accounted for by the increased time taken by the AN group to
complete the task, which increased accuracy. This contrasts with Grunwald et al. [26] finding, where the groups took an equal amount of time. The AN group in this study
were more inaccurate on the task than in Grunwald et al. [26] study, but the HC group were also more inaccurate, comparable with the AN group.
This may point to a more impulsive and therefore inaccurate style within the HC group.

In accordance with our hypothesis the AN group reported significantly higher levels
of perfectionism compared to controls.

In addition, associations between body image dissatisfaction, perfectionism, haptic
perception and body image distortion were explored. There was no evidence to support
a relationship between the haptic perception tasks and the body size estimation task,
thus failing to support the hypothesis that fundamental haptic perception ability
affects body distortion in AN. However, all the attitudinal, self-report measures
were significantly correlated with body image distortion. Body dissatisfaction showed
the strongest negative relationship – the smaller the desired silhouette than the
actual, the greater the overestimation of body size, which supports Cash and Deagle’s
[48] proposal that body overestimation may contribute to body dissatisfaction, though
we can make no claims as to the direction of the relationship between the two. This
links the concepts of dissatisfaction and distortion in individuals with AN, despite
proposed separate neural correlates of each [49].

Overall, the positive relationships between body dissatisfaction and perfectionism
with body size estimation in the AN group would suggest that attitudes (cognitions
and affect) and behaviours are significantly related to body image distortion in AN.

The findings suggest that attitudinal factors and perfectionism are related to body
distortion, but that there is no significant relationship between body distortion
and haptic perceptual performance, at least as measured on a ‘neutral’ task involving
haptic perception. This suggests that there are no fundamental haptic perceptual problems
underlying body image disturbances in AN, but does not negate findings of sub-optimal
visual perceptual performance in AN. Nor does it negate findings of parietal lobe
dysfunction in AN (e.g. [29]), related to body image issues, which may involve difficulties in integrating sensory
information from different modalities, rather than separate deficits in perception
per se, as suggested by Case et al. [34] in their investigation of performance on the size-weight illusion task. In this context,
it may be that haptic perception in individuals with AN is intact, at the fundamental
level, but is overridden by an increased sensitivity to visual input, as seen in the
rubber hand illusion [50], which then leads to a visual distortion of body image, and a lack of attention to
proprioceptive or interoceptive information. Equally, it may be that body dissatisfaction
impacts on the visual mental image of the body, which then also affects tactile perception
when related to one’s own body, as suggested by Keizer et al. [10]. It will be of interest to use such “body-related” measures in future research to
determine if a more salient focus does have an effect.

The strengths of this study are that, compared to previous work in the field, the
two components of body image were measured separately, rather than treating them as
a unitary concept. Confounding body dissatisfaction and body distortion has been argued
to be a reason for mixed findings in the literature [49]. The haptic perception task provided a ‘neutral’ measure of fundamental somatosensory
perception, divorced as far as possible from body attitudes. The BSE task, whilst
not free from attitudinal biases, was intended to give as clear a picture of body
image distortion as possible, including re-evaluation of the completed gestalt silhouette,
and avoiding the use of distressing images of the individual. Coupled with self-report
measures, this was intended to give as rounded a picture of body image disturbance
as possible.

Some limitations must be considered. Firstly, the AN group spent significantly longer
on the haptic perception task compared to the HC group, which may have allowed them
to be more accurate than they would have been if there was a time limit imposed. Secondly,
analyses of the angle paradigm task were found to be underpowered (post hoc analysis)
which may explain non-significant findings.

Future research should replicate the Angle Paradigm Task performance in AN (and its
subtypes) compared to HC with greater numbers as this study may have been underpowered
in this domain. Given that the AN group took longer to complete this task, a time
limit would be useful to determine any impact on accuracy. The use of both uni- and
bi-manual tasks would assist in identifying performance related to sensory integration,
and to haptic perception. A battery of haptic tasks with and without visual feedback
would also clarify the picture of sensory processing in the disorder, as would comparison
of ‘body-neutral’ tasks, with ‘own-body focused’ paradigms, likely to activate different
bodily representations. Further exploration of the role of perfectionism in body image
disturbance is warranted, and whether this relates to a subgroup of individuals with
obsessive-compulsive traits. It will be useful to relate this to the specific perfectionism
dimensions linked to eating disorder symptomatology, and then to body dissatisfaction
and distortion in particular.

Clinically, this study highlights the role of cognitive behavioural interventions
in modifying beliefs relating to body image and the use of exposure (behavioural tasks,
mirror exposure) in addressing body size distortion (see [51-53]). Additionally, given the high levels of perfectionism and its association with body
distortion, techniques which focus on acceptance (e.g. mindfulness; [54]) or on adapting CBT for clinical perfectionism [55] with specific reference to body image may be beneficial.

Conclusion

Findings did not confirm the presence of fundamental haptic perceptual impairments
in body image distortion in individuals with AN. Future work should explore whether
or not previous findings in the literature demonstrating sub-optimal visual perceptual
performance in AN could contribute to body image distortion. The findings did confirm
the strong relationship between body image disturbance and cognitive-affective factors.
This highlights the importance of continuing to focus on treatment interventions that
target cognitive-affective biases and high levels of perfectionism as opposed to correcting
underlying fundamental perceptual inefficiencies.

Competing interests

The authors declare that they have no competing interest.

Authors’ contributions

AW - Conceived and designed the protocol, conducted experiments, analysed the results,
drafted the paper. RL - Conducted the experiments, took part in analysis, revision
of the paper. VM – co supervised the project, participated in planning the study and
revised the paper. KT – principal investigator, planned the study protocol, helped
with the participant recruitment, supervised the project, edited drafts, submitted
the paper. All authors read and approved the final manuscript.

Acknowledgments

Dr. Kate Tchanturia would like to acknowledge funding from the NIHR Biomedical Research
Centre for Mental Health at South London and Maudsley NHS Foundation Trust and Institute
of Psychiatry, King’s College London and the Swiss Anorexia foundation for their support.